In recent years, a ferromagnetic tunnel junction element has been the focus of attention because of its potentially high MR ratio. Thus, it has been developed actively for applications to devices such as a magnetic head and a magnetic random access memory (MRAM). When used as a memory, the element allows information to be written by changing the magnetization direction of at least one of the ferromagnetic materials that constitute a ferromagnetic tunnel junction and allows the information to be read by detecting a change in resistance resulting from the change in magnetization direction.
To meet the demand for mass storage, the element and conductive wires for writing/reading should be reduced to submicron in size. It is expected that further progress in miniaturization will increase a magnetic field required to change the magnetization direction of the ferromagnetic material. However, there is a limit to the current flowing through the miniaturized conductive wires. Therefore, it is necessary to apply a magnetic field efficiently to a magnetoresistive element.
U.S. Pat. No. 5,659,499 proposes the use of a magnetic member placed around conductive wires for the application of a magnetic field to a magnetoresistive element. However, this configuration fails to consider the fact that the size of the ferromagnetic member also is restricted by miniaturization of the element. In particular, when the ferromagnetic member is placed along a conductive wire whose width is restricted, the shape anisotropy, e.g., in the direction of drawing of the conductive wire prevents the efficient application of a magnetic field.
It is favorable that the conductive wires for writing are located closer to the magnetoresistive element to apply a magnetic field efficiently because the magnetic field is attenuated with the square of the distance. When a three-terminal element such as a MOS transistor is used as a switching element of the memory, an extraction conductive wire is needed to connect the magnetoresistive element and the switching element. Therefore, one of the conductive wires for writing has to apply a magnetic field to the element from beyond this extraction conductive wire. When a diode is used as a switching element and placed between the magnetoresistive element and the conductive wire for writing and reading, this conductive wire also has to apply a magnetic field to the element from beyond the switching element.
Another problem to be solved for the achievement of mass storage is crosstalk due to high integration of an element. The crosstalk causes malfunction or the like of elements that are adjacent to the element to which a magnetic field should be applied.